AC_LANG and _AC_LANG_ABBREV (fwd)

[Travis Shirk]

Hello,

I've run into a problem while porting my autoconf scripts
from 2.13 to 2.52.  I used the following m4 code in one of
my scripts:

ifelse(AC_LANG,C,AC_REQUIRE([AC_PROG_CC]))

This works in 2.13 because AC_LANG_C defines AC_LANG to C,
but 2.52 defines AC_LANG much differently and 'autoheader'
fails when processing my code.  I'd like to delay using
AC_PREQ([2.52]) until the rest of my team can upgrade, but is
there anyway to have a version of my macro that will support
both versions?  I've tried using nested ifelse statements in
conjunction with AC_ACVERSION to no avail.  m4 always want
to expand the AC_LANG macro even when the ifelse evaluates
around it.

I also noticed that autoconf 2.52 contains a macro called
_AC_LANG_ABBREV.  Is this how I should implement this type
of thing in 2.52?  Does the preceeding '_' mean that the
function is for internal use only?

Travis